Marangoni Flow Diagnostic Assay for Salt Interference

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Solution Overview

Problem

Current diagnostic assays for detecting biomarkers, such as the malaria biomarker protein Plasmodium falciparum histidine-rich protein II, face challenges including the need for precise alignment over a magnetic field, limited sensitivity, and interference from salt crystals leading to false results in physiologic conditions.

Innovation Solution

A method utilizing a sample with a salt or sugar and a hygroscopic material/surfactant in an aqueous liquid carrier, combined with capture particles that aggregate upon analyte presence, placed on a non-permeable substrate with low thermal conductivity to promote inward Marangoni flow, concentrating aggregates at the droplet center for detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If primary radial flow is used to organize particles, then particle organization occurs, but the assay requires precise alignment over a magnetic field and has limited sensitivity

Engineering Contradiction:

Improvedetection sensitivityVSAvoidalignment requirement

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces the magnetic field alignment mechanism with a surface tension-based Marangoni flow system. Instead of using magnetic forces to organize particles, the invention uses evaporative surface tension gradients to drive fluid flow that naturally concentrates particle aggregates at the drop center, eliminating the need for precise magnetic field alignment while improving detection sensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the flow regime parameter from primary radial flow to Marangoni flow by controlling evaporation conditions and surface tension gradients. This parameter change transforms the flow pattern to achieve both high sensitivity and operational simplicity without magnetic alignment requirements

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If evaporation proceeds to completion, then particle concentration increases, but salt crystallization occurs causing false results

Engineering Contradiction:

Improvedetection sensitivityVSAvoidsalt crystallization interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of salt crystallization into a beneficial outcome by using controlled partial evaporation. The Marangoni flow driven by surface tension gradients achieves sufficient particle concentration before complete evaporation occurs, preventing salt crystal formation while maintaining high detection sensitivity through the inward flow pattern

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of operation

If drop volume is reduced for simplicity, then operation becomes easier, but detection sensitivity decreases

Engineering Contradiction:

Improveassay simplicityVSAvoiddetection sensitivity

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent uses evaporative fluid dynamics and surface tension forces to concentrate particles in a controlled manner during drop evaporation. The Marangoni flow mechanism efficiently concentrates particle aggregates at the drop center, achieving high detection sensitivity in small volume drops without requiring complex instrumentation or large sample volumes

Inventive Principle:

Principle #29Pneumatics and hydraulics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances sensitivity by approximately 1000-fold, operates effectively in physiologic salinity conditions without requiring magnetic field alignment, and prevents salt crystallization, providing a simple and accurate diagnostic method.

Implementation Method 1

Fluid flows in a radial direction to replenish solution preferentially lost at the edge where solvent molecules evaporate at the greatest rate. The resulting flow fields include the primary radial flow and secondary flows caused by direct and indirect effects of the non-uniform evaporation rate

Methodology Applied

Scientific EffectMarangoni flow: Marangoni Effect

Implementation Method 2

placing a droplet of said liquid sample in step (b) on a non-permeable substrate, wherein the thermal conductivity of the substrate is less than 1.6 times that of the liquid sample

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS10101323B2Liquid diagnostic assays utilizing marangoni flow

Publication Date: 2018.10.16 VANDERBILT UNIV

AI summary

The present invention provides simple and inexpensive assays for the detection of virtually any analyte in any sample that is in liquid form or that can be solubilized. The assays utilize the fluid dynamics of drop evaporation whereby soluble materials, including analytes and particles binding thereto, are drawn to the center of the drop by Marangoni flow and ultimately form a concentrated residual spot. The presence or absence of certain reagents can then be detected through a number of different approaches.